The present invention relates to a method for the regulation of the mixture composition in a mixture-compressing internal combustion engine which includes one fuel-injection valve per cylinder unit arranged in the associated suction channel and controllable by an electronic control unit.
In present-day mixture-compressing internal combustion engines having an electronically controlled fuel-injection system (for example, L-Jetronic), whose exhaust gas is after-treated by way of a catalyst, it is customary to regulate the mixture composition by way of a lambda probe arranged in the exhaust gas line of the internal combustion engine. This lambda probe entails the disadvantage that it operates only after it has reached its operating temperature by the exhaust gas or by means of a heating element. If, in order to improve this disadvantage, it is arranged in direct proximity of the internal combustion engine, the danger exists that it may suffer damages as a result of the occurring exhaust gas peak temperatures. Therebeyond with the use of only one lambda probe in the exhaust gas manifold, only the mixture composition for all cylinders can be regulated simultaneously.
The present invention is therefore concerned with the task to provide a method of the type described above in which the use of a lambda probe can be dispensed with.
The underlying problems are solved according to the present invention in that directly after the start of the internal combustion engine, the mixture is initially enriched or leaned down for each cylinder unit and that subsequently the change of the energy pulse between two successive ignitions which is introduced into the crankshaft of the internal combustion engine by an ignition or a parameter corresponding to this magnitude is continuously determined and in that the mixture is then enriched in the case that the amount of the respectively determined energy pulse change lies above a predetermined shifting-comparison value dependent on an operating parameter, and otherwise is leaned down.
The mixture regulation can be carried out with the method according to the present invention, in which a lambda probe can be dispensed with, already directly after the start of the internal combustion engine and more particularly separately for each cylinder so that eventually occurring errors in the air or fuel distribution onto the individual cylinders are immediately compensated for. The control for carrying out the method can be integrated without any problem into the control electronics already present in an electronic fuel injection system so that the realization of the method is connected only with relatively slight costs. A further advantage of the method of the present invention resides in that it can be used not only for the regulation to a stoichiometric mixture composition but also for the regulation of the mixture to the lean limit.